| 摘要 |
PURPOSE:To prevent breakage of an operational amplifier even when a connector is reversely connected in error and against a sensor circuit device plus/minus of a power source are reversely connected by mounting resistance on the power supply line of the operational amplifier. CONSTITUTION:When an output terminal 13-3 in a bridge circuit 13, is higher than an output terminal 13-4 in potential positive side input 14-3 in an operational amplifier 14 is higher than negative side input 14-4 in potential and potential of output terminal 14-5 of the amplifier 14 is raised and base current IB of a transistor 15 is increased. Hereby, collector current ICE is increased and current flowing through resistances R11,R12 is increased, and potential at connecting point of resistances R11,R12 is dropped by voltage drop generated in resistance R11 by increased collector current ICE. Then, potential of positive side input 14-3 of the amplifier 14 is actuated to lower, and the transistor 15 amplifies output of the amplifier 14 and also applies negative feedback on the output of the amplifier 14. Meanwhile, even when pulse/minus of the power source is reversely connected at wiring, by deciding resistance values r13,r14 so as to establish the relation : Ir>Vcc/r13+r14>I14 against endurance current Ir to reverse connection of the amplifier 14, the amplifier is not broken. |
